The truth is still out there, as more than 20 million viewers who watched “The X-Files” premiere on Jan. 24 can tell you.

In addition to returning Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson), the revived Fox series brings back memorable characters like Walter Skinner and the Cigarette Smoking Man (aka “Cancer Man”) and introduces a handful of new guest stars. Ahead of Episode 3 (airing Monday at 8 p.m.), The Post asked those actors to weigh in on their “X-Files” experience.

How did it feel to be back in the world of “X-Files”?

Mitch Pileggi (Walter Skinner): “Returning to the show and this character felt normal, felt right. It felt like there had been a very long weekend and it was Monday and we were back to work. I guess when you do a show like this for so many years, it becomes such a part of you and with the revival something inside of me said, ‘Hey Walter, put your suit and specs on. It’s time to go to the agency.’ ”

What’s the best “X-Files” fan interaction you’ve had?

Robbie Amell (FBI Agent Miller): “The weekend I got back from filming, I went for a beer with a buddy. The bartender served us our drinks and said ‘Have a nice night Agent Miller,’ followed by the DJ turning on the ‘X-Files’ theme music. That was based off of a casting announcement. The fans are next-level.”William B. Davis (Cigarette Smoking Man): “Fans would sometimes write to me and occasionally a correspondence would develop. One correspondence became more interesting and finally led to a meeting when I was in London for a convention — she was French. We have now been happily married for almost five years.”

What’s your most memorable moment from filming?

Rhys Darby (Guy Mann): “When you see my episode you’ll understand that as a fan I had the ultimate ‘X-Files’ trip. I don’t want to give anything away, but at one point I even melee with Mulder. I cut my hand on a smashed bottle and still have the scars to prove it.”

Did you take a souvenir from the set?

Lauren Ambrose (Agent Einstein): “I took a selfie in front of Mulder’s office door. I don’t really know why I did this — I lost my mind and totally nerded out. The crew was laughing at me.”Annabeth Gish (Monica Reyes): “The set decorator hung a beautifully woven strand of tiny bells and beads on Monica’s [apartment] door. I still have it hanging on one of my doors at home.”

What did you do to prepare for filming?

Annet Mahendru (Sveta): “I binged ‘The Fall’ [starring Anderson], watched a meteor shower and imagined giving birth to half-aliens.”Joel McHale (Tad O’Malley): “I shaved, which is something that I haven’t done in years. I felt naked and exposed and I decided that was a good for my character. So good, I went ahead and shaved every hair off of my body including my eyebrows and eyelashes. Then I was officially prepared in my mind to play a conservative talk show host. (Most talk radio hosts do this regardless of political preference.”)